1. Field of the Invention
This invention concerns uniquely pinned dental die models, i.e., positive moldings of teeth and associated gum area, and their preparation and use, and particularly concerns the means and method for providing easy and convenient access to the free ends of the conventionally employed locator dowel pins for selective removal of segments of the cut die model with their associated dowel pins affixed thereto.
2. Description of the Prior Art
In the field of tooth or plate reconstruction, die models of teeth and associated gum portions are typically employed for making the prosthodontic appliances such as bridgework, crowns, plates, individual teeth and the like. This is done by forming an impression mold out of a quick-setting impression material such as plaster of paris around the actual teeth and associated gum portions or areas of the patient which duplicates as a negative molding or impression the patient's teeth and gum portions. Thereafter, the negative molding of the teeth and gum portions is converted to a positive molding from the impression, which positive molding or die model is then utilized in the construction of the dental prosthesis.
In a typical conventionally used procedure, as depicted in FIGS. 12 and 13, after molding of the die model 11, the posterior face 13 of the reproduced gum portions or base 15 is sanded flat and several dowel pins 17, typically made of brass, are inserted into holes 19 drilled into the die model base from said posterior face and adhesively secured therein. Typically at least one hole and pin are employed for each segment 21 to be cut from the die model.
To facilitate the cutting of the die model into said segments and for providing a support 25 from which and upon which the segments can be removed and replaced respectively in proper relative positions, it is conventional that prior to cutting, the die model is positioned over the support 25 comprising a mass of partially cured material such as plaster of paris positioned on a flat surface 27 and which is approximately the consistency of dough. The dowel pins are then forced into the dough-like material of the base support at its proximal surface 29 such that the posterior face 13 of the die model base comes to rest on the proximal surface 29 of the support of partially cured material. The posterior face 13 of the die model base is generally treated with a separating medium or releasing agent to prevent adhesion to the support during the cure of the support. Material is then allowed to harden around the pins, after which the posterior surface 35 thereof is ground or otherwise formed into an appropriate configuration for being received e.g., by an adaptor member such as 39 shown in dotted line, of an articulator, e.g., a configuration roughly of the lateral dimensions and shape of the die model, for duplication of jaw action as the dental prosthesis subsequently is shaped in accordance with the die model.
After hardening of the support material, the die model, while still pinned to the, support by means of the sockets 41 formed in the support can be cut into various separate segments 21 as desired. The individual segments, each carrying one or more dowel pins, are then selectively removed from the support and from the rest of the die model and positioned in work apparatus or hand-held for further forming operations. Thereafter, the segment may be replaced in proper position on the support and retained thereon by the said one or more dowel pins which are reinserted into their sockets which were formed in the support material upon curing. The pins thus precisely reposition the separate segments relative to the rest of the die model.
With reference to the above description of prior practices, a tedious and time consuming problem exists, with respect to preparing the combination of (1) die model, i.e., positive die stone replication of teeth and associated gum areas and having dowel pins affixed thereto, and (2) a support to which the die model is removably affixed by said dowel pins being inserted into the sockets formed in the support. The problem arises from the fact that the dowel pins are first positioned in the uncured base material which is then hardened around the pins. This process gives a significant frictional or adhesive attachment of the support to the pins and requires that the free ends 43 of the pins be accessible from the posterior surface 35 of the support such that force can be applied to said free ends in order to drive the pins out of their sockets and separate the entire die model or segments thereof from the support.
Heretofore, the technique of choice for exposing the free ends of the pins has been to chip or cut away the areas 51 of said support shown in dotted line in FIG. 13, at its posterior surface 35 immediately surrounding said free ends in order to expose sufficient portions of said free ends to allow engagement thereof with an impact or other force providing tool to drive the pins from their sockets. This chipping or cutting is laborious, tedious and time consuming, and produces a product of crude and displeasing appearance. Also employed is the technique of molding the support material around the pins such that the free ends thereof extend outwardly from the posterior surface of the support and are thus automatically exposed. This construction however, in many situations, cannot be used, such as where the support itself must sit flat on a surface of an articulator casting or adaptor member such as 39 or other foundation means.
Exemplary of the prior art which discloses such use of locator dowel pins and a supporting structure for the die model segments are the following U.S. Pat. Nos.: 4,398,884; 3,937,773; 4,078,310; 4,265,619; 4,721,464; and 4,917,347, the general disclosures of which regarding articulators, casting materials, and dental models and their use are hereby incorporated herein by reference.